Disclaimer: I didn't install this on my server as I custom code my plugins, but I looked through the source code to make this review.

This is very well coded, well optimised. Some things I would add, is a combat tag command to view the current combat tag & time (if any) of yourself or another player. Maybe use the Ersatz addon to set placeholders, so external plugins (e.g. scoreboard plugins) can view the combat tag status and how much longer is left.

TL;DR:
Good skript, i'd use it if I didnt custom code my own plugins. Well done!